Transformers MCQs

Option A: to provide coupling between primary and secondary

Option B: to increase the magnitude of mutual flux

Option C: to decrease the magnitude of mag-netizing current

Option D: to provide all above features

Correct Answer: to provide all above features ✔

Option A: less will be the secondary induced e.m.f.

Option B: less will be the primary induced e.m.f.

Option C: less will be the primary terminal voltage

Option D: none of the above

Correct Answer: less will be the secondary induced e.m.f. ✔

Option A: to provide free passage to the cooling oil

Option B: to insulate the coils from each other

Option C: both A. and (b)

Option D: none of the above

Correct Answer: to provide free passage to the cooling oil ✔

Option A: has high magnitude and low power factor

Option B: has high magnitude and high power factor

Option C: has small magnitude and high power factor

Option D: has small magnitude and low power factor

Correct Answer: has small magnitude and low power factor ✔

Option A: load on it increases

Option B: load on it decreases

Option C: load remains constant

Option D: none of the above

Correct Answer: load on it decreases ✔

Option A: at no load

Option B: at 50% full load

Option C: at 80% full load

Option D: at full load

Correct Answer: at 50% full load ✔

Option A: nearly full load

Option B: 70% full load

Option C: 50% full load

Option D: no load

Correct Answer: nearly full load ✔

Option A: 3000 kVA

Option B: 1000 kVA

Option C: 500 kVA

Option D: 250 kVA

Correct Answer: 3000 kVA ✔

Option A: provide fresh air for cooling the transformer

Option B: supply cooling oil to transformer in time of need

Option C: protect the transformer from damage when oil expends due to heating

Option D: none of the above

Correct Answer: protect the transformer from damage when oil expends due to heating ✔

Option A: supply frequency

Option B: load current

Option C: power factor of load

Option D: both B. and (c)

Correct Answer: D. both B. and (c) ✔

Option A: 180°

Option B: 120″

Option C: 90°

Option D: 75°

Correct Answer: 90° ✔

Option A: natural air cooling

Option B: air blast cooling

Option C: oil cooling

Option D: any of the above

Correct Answer: oil cooling ✔

Option A: friction and windage losses

Option B: copper losses

Option C: hysteresis and eddy current losses

Option D: none of the above

Correct Answer: hysteresis and eddy current losses ✔

Option A: 100 per cent

Option B: 98 per cent

Option C: 50 per cent

Option D: 25 per cent

Correct Answer: B. 98 per cen ✔

Option A: Low voltage winding

Option B: High voltage winding

Option C: Primary winding

Option D: Secondary winding

Correct Answer: High voltage winding ✔

Option A: is always a low voltage winding

Option B: is always a high voltage winding

Option C: could either be a low voltage or high voltage winding

Option D: none of the above

Correct Answer: could either be a low voltage or high voltage winding ✔

Option A: there is no need to change the D.C. voltage

Option B: a D.C. circuit has more losses

Option C: Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is zero

Option D: none of the above

Correct Answer: Faraday’s laws of electromagnetic induction are not valid since the rate of change of flux is zero ✔

Option A: voltage

Option B: current

Option C: power

Option D: frequency

Correct Answer: power ✔

Option A: Low voltage winding

Option B: High voltage winding

Option C: Primary winding

Option D: Secondary winding

Correct Answer: Low voltage winding ✔

Option A: High voltage side

Option B: Low voltage side

Option C: Primary side

Option D: Secondary side

Correct Answer: Low voltage side ✔

Option A: Conservator

Option B: Breather

Option C: Buchholz relay

Option D: Exciter

Correct Answer: Exciter ✔

Option A: provide support to windings

Option B: reduce hysteresis loss

Option C: decrease the reluctance of the magnetic path

Option D: reduce eddy current losses

Correct Answer: decrease the reluctance of the magnetic path ✔

Option A: lags behind the voltage by about 75°

Option B: leads the voltage by about 75°

Option C: lags behind the voltage by about 15°

Option D: leads the voltage by about 15°

Correct Answer: lags behind the voltage by about 75° ✔

Option A: copper losses = hysteresis losses

Option B: hysteresis losses = eddy current losses

Option C: eddy current losses = copper losses

Option D: copper losses = iron losses

Correct Answer: copper losses = iron losses ✔

Option A: 1.7 Wb/m2

Option B: 2.7 Wb/m2

Option C: 3.7 Wb/m2

Option D: 4.7 Wb/m2

Correct Answer: 1.7 Wb/m2 ✔

Option A: temperature

Option B: stray losses

Option C: all-day efficiency

Option D: none of the above

Correct Answer: temperature ✔

Option A: lkV

Option B: 33 kV

Option C: 100 kV

Option D: 330 kV

Correct Answer: 33 kV ✔

Option A: copper loss

Option B: magnetising current

Option C: magnetising current and loss

Option D: efficiency of the transformer

Correct Answer: magnetising current ✔

Option A: high resistance

Option B: high reluctance

Option C: low resistance

Option D: low reluctance

Correct Answer: low reluctance ✔

Option A: 0.2 to 0.5 per cent

Option B: 2 to 5 per cent

Option C: 12 to 15 per cent

Option D: 20 to 30 per cent

Correct Answer: 2 to 5 per cent ✔

Option A: tightness of clamping

Option B: gauge of laminations

Option C: size of laminations

Option D: all of the above

Correct Answer: all of the above ✔

Option A: reduce hysteresis loss

Option B: reduce eddy current losses

Option C: reduce copper losses

Option D: reduce all above losses

Correct Answer: reduce eddy current losses ✔

Option A: through cooling coil

Option B: through air

Option C: by the flux

Option D: none of the above

Correct Answer: by the flux ✔

Option A: Current

Option B: Voltage

Option C: Frequency

Option D: All of the above

Correct Answer: Frequency ✔